* Control statements
*** Outline
***** Introduction
******* What are we going to do?
******* How are we going to do?
******* Arsenal Required
********* working knowledge of arrays

*** Script
    Welcome. 
    
    In this tutorial we shall be covering conditional statements and
    control loops. We have used them already in some of our previous
    sessions with brief introduction. We shall be covering 'if-else' 
    statement, 'while' and 'for' loops.
    For understanding of conditional statement we will write a python
    script. Open Scite text editor by going to Applications->
    Programming->Scite:
    First we prompt user for entering a integer by using raw_input
    x = int(raw_input("Enter an integer: "))
    we convert the input string to 'int'
    if x < 0:
    We check if number is less then zero
        if condition is true we print 
        print 'Be positive!'	
	note the indentation
    elif x == 0:
        This is else-if condition and corresponding message
	end of previous indentation indicates ending of a block
        print 'Zero'
    elif x == 1:
        print 'Single'
    else:
        This is else block which is executed when all if, and else
	if statements fails.
        print 'More'
    Save this script in home folder with name '.py'	
    To run this script inside IPython we first start interpreter and 
    type 
    %run '.py'
    It will prompt us to enter a integer and based on our input it 
    prints appropriate message. 

    Python supports only if-elif-else conditional constructs, 
    switch-case statements are not available/supported in Python.
    We can use binary operators like and/or/not to check for multiple
    conditions.

    Now lets look at loop constructs available. Python supports 'while'
    and 'for' statements. We will write a script to understand 'while'
    statement. In Scite click on 'new' file shortcut to open a new tab
    We shall write a script for printing all fabonacci numbers less then
    10. In this series Sum of previous two elements defines the next 
    element.
    
    First we initialize two variable to first and second number of 
    series
    a, b = 0, 1
    while b < 10:
        This block will be executed till this condition holds True
        print b,
	Note ',' here for printing values in one continues line.
	a, b = b, a+b
	This is one powerful feature of Python, swapping and assigning
	new values at the same time. After this statement a will have 
	present 'b' value and b will have value of 'a+b'(phew this can be close)
	
    Save this file as 'fabonacci.py' and lets run it from IPython 
    interpreter by
    %run fabonacci.py

    'for' in python works any kind of iterable objects. In our 
    previous sessions we used 'for' to iterate through files and lists.
    So in case we want to get square of say first five numbers using 
    'for' loop, we will have to create a list. For this we will use 
    'range' function available. Lets take a look at documentation 
    available for 'range' function by typing
    range?
    It takes three arguments, first being the start/initial value
    second one being stop/last value and third being the step size. 
    Out of these 'start' and 'step' arguments are optional.
    So if we use range to get first five number it would be 
    range(5)
    Note here that last/stop value is not included in resulting 
    list. So to get square of first five number all we have to do is
    iterate over this list.
    for i in range(5):
    ....print i, i*i
    ....
    ....
    Similarly to get square of all odd numbers from 3 to 9 we can do 
    something like

    for i in range(3, 10, 2):
    so the list returned from range this time will start from 3 and 
    end at 10(excluding it) with step size of 2 so we get odd numbers
    only
    ....print i, i*i
    ....
    ....
        
    That brings us to the end of this tutorial. We have covered more
    details on conditional statements in Python. How to write loops
    using 'while' loops. Range function and using for loop with range

    Thank you!

*** Notes